A multinational force under the command of Count Raymond Berengar IV of Barcelona besieged the city of Tortosa (Arabic Ṭurṭūsha), then a part of the Almoravid Emirate, for six months before the garrison surrendered.

The most detailed source for the siege is the short History of the Capture of Almería and Tortosa by the Genoese statesman Caffaro di Rustico.

[1] Besides Caffaro's work, the Genoese state archives contain valuable documents about events immediately preceding and succeeding the siege, such as the treaty with the count of Barcelona.

[7] In 1116, Raymond Berengar III negotiated aid from Genoa and Pisa, and received explicit papal approval for an attack on Tortosa that never came to fruition.

[12] In 1146, a fleet from Genoa under the consul Caffaro di Rustico launched an attack on the Almoravid-held island of Menorca, then crossed over to the mainland to besiege the city of Almería, which was forced to pay a tribute.

[17] On 5 October 1146, Pope Eugenius III issued the bull Divina dispensatione I encouraging Italian participation in the Second Crusade.

[18] On 22 June 1147, Eugenius issued another bull calling upon Christians to assist the count of Barcelona "in the expulsion of the infidels and the enemies of the cross of Christ" (ad expugnationem infidelium et inimicorum crucis Christi).

[11] As an Englishman, Nicholas might have been instrumental in convincing Balluini de Carona, the leader of the Anglo-Norman contingents, about the worthiness of the enterprise.

[5] It is probable that some or all of the English, Flemish and Norman crusaders were veterans of the Lisbon campaign, although another portion of that Anglo-Flemish army had gone on to the Holy Land and was at that time participating in the siege of Damascus.

The only source to explicitly link the English at Tortosa with those at Lisbon is the Royal Chronicle of Cologne, which says that afterwards they continued on to the Holy Land.

These three orders were the beneficiaries of Alfonso the Battler's will, which had been ignored after his death in favour of the succession of Ramiro II, father of Raymond Berengar's wife, Petronilla.

From Barcelona, two galleys bearing two of the consuls returned to Genoa with money from the booty of Almería to pay off some of the city's debts.

[6] The campaign may have been delayed by the ongoing dispute between Raymond Berengar and King García Ramírez of Navarre,[b] who appears to have taken the opportunity to seize the Aragonese town of Tauste in March.

[16] The Genoese fleet was under the command of the consuls Oberto Torre, Filippo di Platealonga, Balduino and Ansario Doria and Ingo and Ansaldo Piso.

Half of the Genoese army, augmented by some Catalan knights, encamped on the riverbank just outside the outer town walls to the south.

The rest of the Genoese, the Catalans and Occitans under the personal command of Raymond Berengar and his seneschal, Guillem Ramon II de Montcada, camped above the city on the hill called Banyera to the northeast.

The military orders and the crusader contingents from England, Normandy and Flanders camped beside a mill on the river just north of the town.

[5][8][6] Unfortunately for the garrison of Tortosa, the Muslim ruler to the immediate south, Ibn Mardanīsh, was tied by treaty to Raymond Berengar.

[5] As a later charter put it: "Tortosa, the key of the Christians, the glory of the people, an ornament of the whole world, was captured" (Capta est Dertosa, clavis Christianorum, gloria populorum, decor universae terrae).

After the surrender, the cemetery was handed over to the Canons of the Holy Sepulchre, so that in death the pilgrims could in a sense fulfill their vows to go to Jerusalem.

[26] Tortosa was taken with minimal bloodshed, probably because previous experience with Tarragona had shown how difficult repopulating a city with Catalans could be.

The remainder went to Raymond Berengar, who granted a fifth of the revenues from the countryside and the outlying castles to the Templars, who were charged with maintaining a defensive perimeter.

[5] In 1150, the Genoese third was under the control of Balduino di Castro and Guglielmo Tornello, but in 1153 the city sold its share of Tortosa to Raymond Berengar for 16,000 maravedíes.

[27] Following the capture of Tortosa, Raymond Berengar led a re-enforced army some 90 kilometres (56 mi) inland to besiege Lleida in the spring of 1149.